Liquid storage containers blow-molded from polyesters, particularly poly(ethylene terephthalate) are easily fabricated at reasonable cost and have received wide acceptance in the market place as containers suitable for storing many liquids. The use of such polyester containers to package liquids having a sensitivity to oxygen or liquids requiring internal pressurization by the addition of carbon dioxide has been somewhat restricted, however, by reason of the fact that most polyesters, and particularly poly(ethylene terephthalate), allow significant ingress of environmental oxygen and significant egress of carbon dioxide to and from the package contents. In many circumstances like soft drink packaging, beer packaging and wine packaging, the barrier characteristics have significantly reduced the utility of polyester based containers.
In the past, a number of approaches have been used to attempt to solve the poor barrier properties of polyester resins. Various barrier polymers have been admixed with polyesters in an attempt to improve container performance. Unfortunately, resin expense or only marginally superior results in respect of physical properties and barrier characteristics compared to native polyesters have been experienced. Notably, such admixtures show significant moisture sensitivity and are not optically clear when blow molded.
Similarly, many chemically modified polyesters have been developed in an attempt to overcome the relatively poor barrier properties of the polyesters by adding various functional groups to the polymer chain. Unfortunately, costs, or processing characteristics, poor barrier properties or poor mechanical strength have significantly reduced the acceptance of these materials in the market place.
Accordingly, there is a need in the art for an improved polyester-based resin blend which is capable of being injection-molded, providing a high gas and water vapor transmission barrier, excellent mechanical properties, low sensitivity to barrier performance loss when exposed to moisture, low acetaldehyde levels upon processing for use of foodstuffs as well as being optically clear when blow-molded and capable of being strain-hardened upon molecular orientation by blow-molding.